In the fabrication of industrial use steel containers, such as 55 -gallon drums, it is most important that the joint between the pressed-in threaded closure flange and the surrounding container wall be properly gasketed. In order to adequately assure that a sealing gasket has been properly applied to the closure flange prior to insertion of the flange within the drum stock opening, an accurate fail-safe inspection operation is required. Moreover, to provide maximum protection against failure, it is not uncommon to inspect the closure flange for gasket presence at the final step in the flange manufacture as well as just prior to inserting the flange within the container wall during the drum fabrication.
A number of gasket detecting schemes have been employed in the past with varying degrees of success. Most of these prior attempts, however, have either involved relatively complex mechanisms which are inherently costly and troublesome or have in some way disturbed the gasket during the sensing operation introducing an additional unwanted variable. The problem is one of performing the above described inspection operation in a simple efficient manner readily adaptable to various flange handling situations.